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richidoo
2006-01-11, 20:11
Got my SQB yesterday. It is awesome. I used it today to audition a reference CD of a record I had mastered. It plays far more accurate and musical than my consumer universal player, that's for sure.

My integrated tube amp blew something in its guts just in time to miss the SQB startup. My tech lent me a pair of Quad Two-Forty tube monoblocs. They are 40wpc, which should make my 95db sensitivity speakers play very loudly at their full power output.

When SQB is driving them, it is loud enough for classical and jazz, but I am at setting 36 for normal to loud listening. Full volume is not as painful as it should be. I am using the SQB volume control connected analog straight into the power amps.

These Quad amps have rated sensitivity of 1Vrms. The SQB3 has rated analog output of 6Vpp, which is 2.1Vrms. I should be driving the Quads to full output and then some. My own amp is only 43 wpc and plays much, much louder. The Quads are not really even breathing at SQB max volume.

To the point, how do I verify that my SQB is indeed putting out 2Vrms? I want to use it without preamp but I want to know it can drive an amp before I buy any new gear for it.

I measured across one analog output with 0dB test tones playing at SQB volume setting 40 through entire freq band. V read .4V and gradually decreased to .09V and falling. Then I realized I was giving the SQB no resistance to drive, so the readings are BS. Can I just hang a 100K resistor in series and measure the output voltage across signal and ground of analog out?

Anoyone ever measured SQB output?
Thank you
Rich

ceejay
2006-01-12, 01:21
My recollection of posts here is that more people have been complaining that their SBs are too loud, rather than too quiet! As a result of this, an option was added recently, which you might want to check... in player settings / audio / preamp volume control you can specify an attentuation value. The default is zero, for full volume, so should be ok, but worth a check in case its been altered while you have been setting up.

Ceejay

richidoo
2006-01-12, 08:54
Yup, attentuation setting is 0, volume 40, no RG.

I discussed it with my friend who loaned the amps to me. Apparently, Quad lowers sensitivity deliberately to increase dynamic range, but that requires that you use a (very) active preamp (15dB gain) to fully drive them.

I have to read up on the meaning of amplifier sensitivity. Still don't quite get it.
Thanks for your reply, CJ
Rich

stinkingpig
2006-01-12, 10:26
....
>
> These Quad amps have rated sensitivity of 1Vrms. The SQB3 has rated
> analog output of 6Vpp, which is 2.1Vrms. I should be driving the Quads
> to full output and then some. My own amp is only 43 wpc and plays much,
> much louder. The Quads are not really even breathing at SQB max volume.
>
>
> To the point, how do I verify that my SQB is indeed putting out 2Vrms?
> I want to use it without preamp but I want to know it can drive an amp
> before I buy any new gear for it.
>
....

There's an audiophiles forum, you'll probably find some information there.
Squeezebox 2 and 3 have the same DAC so if you find SB2 information, it's
applicable.

--
Jack Coates At Monkeynoodle Dot Org: It's A Scientific Venture!
"I spent all me tin with the ladies drinking gin, so across the Western
ocean I must wander" - traditional

seanadams
2006-01-12, 12:53
I measured across one analog output with 0dB test tones playing at SQB volume setting 40 through entire freq band. V read .4V and gradually decreased to .09V and falling. Then I realized I was giving the SQB no resistance to drive, so the readings are BS. Can I just hang a 100K resistor in series and measure the output voltage across signal and ground of analog out?

Anoyone ever measured SQB output?
Thank you
Rich

Make sure you really have a full-scale test tone. There is a built-in test tone which I am certain is correct (reboot and press 3 on the splash screen) which may be helpful. You should see 2V rms. A load resistance is not needed.